Gas wells are developed by drilling a borehole in a formation where the natural gas is believed to exist. The borehole is then fractured by forcing a high pressure liquid, such as water, into the borehole to create fractures throughout the formation and allow the pressurized gas to migrate to the borehole and thus be retrieved at the surface. It often requires a million gallons of water, or more, to carry out the fracturing process. After the formation is fractured, the pressure of the natural gas in the formation is sufficient to cause the gas to migrate from the higher pressure pockets to the lower pressure borehole, and thus to the surface.
Once the gas well begins to produce the hydrocarbon products, the water initially forced down the borehole to fracture the formation, along with water within the formation and the liquid hydrocarbons, are forced to the surface together with the natural gas. The production water that returns to the surface is contaminated with other toxic substances and a significant mineral content, all that must be considered. Traditionally, the production water has been disposed of by hauling it with a tanker truck to a disposal well, or disposed of by even less desirable methods. A disposal well is a special well that is drilled to a deep depth so that the toxic production water pumped therein will theoretically not contaminate aquifers and other sources of ground water.
A technology has been developed by Raymond C. Sherry where the production water from both gas wells and oil wells can be processed at the well site and be disposed of appropriately. See the Sherry U.S. Pat. Nos. 7,963,459; 8,097,128; 8,372,248; 8,602,320 and 8,915,453, which are incorporated herein by reference thereto. These patents generally involve the flash evaporation of the water content of the production water to produce a purified form of water that can be readily reused or otherwise disposed of. The toxic substances and other particulate matter are separated from the water content and disposed of separately. In order to flash evaporate the water content of the production water, a heater is employed to generate the high temperatures necessary to heat the water under a high pressure so that when forced through a specialized variable-size orifice nozzle, the hot water flashes into steam in an evaporation chamber. The steam is subsequently condensed to form the purified form of water.
As is described in the Sherry patents, the gas generated by the gas well is used as the fuel in the burner to heat the production water. The gas can also be employed as a fuel for an engine to drive an AC generator to produce electrical energy required by the water purification system. Any additional AC power that is not used by the purification system can be coupled to the AC power grid to reduce the operational cost of operating the water purification system in the field.
There exists a constant need to make more efficient the water disposal systems, especially when operating in the field and the only source of energy is the hydrocarbon materials that are produced from the oil or gas formations. Accordingly, there is a need to utilize the excess thermal energy that is generated by the system and use it elsewhere to heat various components of the system.